/*
 * libid3tag - ID3 tag manipulation library
 * Copyright (C) 2000-2004 Underbit Technologies, Inc.
 *
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation; either version 2 of the License, or
 * (at your option) any later version.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with this program; if not, write to the Free Software
 * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
 *
 * $Id: util.c,v 1.9 2004/01/23 09:41:32 rob Exp $
 */

# ifdef HAVE_CONFIG_H
#  include "config.h"
# endif

# include "global.h"

# include <stdlib.h>
# include "..\zlibDll\include\zlib.h"

# include "id3tag.h"
# include "util.h"

/*
 * NAME:	util->unsynchronise()
 * DESCRIPTION:	perform (in-place) unsynchronisation
 */
id3_length_t id3_util_unsynchronise(id3_byte_t *data, id3_length_t length)
{
	id3_length_t bytes = 0, count;
	id3_byte_t *end = data + length;
	id3_byte_t const *ptr;

	if (length == 0)
		return 0;

	for (ptr = data; ptr < end - 1; ++ptr) {
		if (ptr[0] == 0xff && (ptr[1] == 0x00 || (ptr[1] & 0xe0) == 0xe0))
			++bytes;
	}

	if (bytes) {
		ptr  = end;
		end += bytes;

		*--end = *--ptr;

		for (count = bytes; count; *--end = *--ptr) {
			if (ptr[-1] == 0xff && (ptr[0] == 0x00 || (ptr[0] & 0xe0) == 0xe0)) {
				*--end = 0x00;
				--count;
			}
		}
	}

	return length + bytes;
}

/*
 * NAME:	util->deunsynchronise()
 * DESCRIPTION:	undo unsynchronisation (in-place)
 */
id3_length_t id3_util_deunsynchronise(id3_byte_t *data, id3_length_t length)
{
	id3_byte_t const *old, *end = data + length;
	id3_byte_t *new;

	if (length == 0)
		return 0;

	for (old = new = data; old < end - 1; ++old) {
		*new++ = *old;
		if (old[0] == 0xff && old[1] == 0x00)
			++old;
	}

	*new++ = *old;

	return (id3_length_t)(new - data);
}

/*
 * NAME:	util->compress()
 * DESCRIPTION:	perform zlib deflate method compression
 */
id3_byte_t *id3_util_compress(id3_byte_t const *data, id3_length_t length,
							  id3_length_t *newlength)
{
	id3_byte_t *compressed;

	*newlength  = length + 12;
	*newlength += *newlength / 1000;

	compressed = malloc(*newlength);
	if (compressed) {
		if (compress2(compressed, (uLongf *)newlength, data, (uLong)length, Z_BEST_COMPRESSION) != Z_OK || *newlength >= length) {
			free(compressed);
			compressed = 0;
		} else {
			id3_byte_t *resized;

			resized = realloc(compressed, *newlength ? *newlength : 1);
			if (resized)
				compressed = resized;
		}
	}

	return compressed;
}

/*
 * NAME:	util->decompress()
 * DESCRIPTION:	undo zlib deflate method compression
 */
id3_byte_t *id3_util_decompress(id3_byte_t const *data, id3_length_t length,
								id3_length_t newlength)
{
	id3_byte_t *decompressed;

	decompressed = malloc(newlength ? newlength : 1);
	if (decompressed) {
		id3_length_t size;

		size = newlength;

		if (uncompress(decompressed, (uLongf *)&size, data, (uLong)length) != Z_OK || size != newlength) {
			free(decompressed);
			decompressed = 0;
		}
	}

	return decompressed;
}
